The present invention relates to a mixer capsule and a mixer unit which includes a mixer capsule, in particular for the production of a dental material.
Mixer capsules which are filled with two or more components in separate chambers by the manufacturer are used to produce mixtures of the components. The components are brought into communication and mixed with one another by the user, for example by the destruction of a wall separating the chambers.
Mixer capsules for the production of dental materials which are often mixed from a pulverulent component and a liquid component, the mixing operation usually taking place in a shaker unit, are known in the dental sector. The fully mixed substance is then discharged directly onto the working area, for example into a tooth cavity, through a discharge spout formed integrally on the mixer capsule.
DE 36 35 574 has disclosed a mixer capsule which is intended for the production of jointing and sealing compounds. In an exemplary embodiment described in this document, an auxiliary chamber which is present in the discharge piston is delimited, on the side which faces the main chamber of the capsule, by a sheet and, on the opposite side, by an auxiliary piston which is arranged displaceably in the discharge piston. In the starting state of the mixer capsule, as well as the second component, a mixer body is accommodated in the auxiliary chamber, which body initially serves to destroy the sheet by manual displacement of the auxiliary piston and then assists with the mixing operation. To allow the reduction in volume which is necessary for displacement of the inner piston together with ball, a gas cushion is provided in the mixing chamber.
In a further embodiment of the known mixer capsule, the mixer ball is initially situated in the main chamber. In this case, the auxiliary chamber which is present in the piston is closed off from the main chamber by means of a cover and on its rear side by a bellows. As a result of manual pressure being applied to the bellows, the cover is pressed away from the piston, so that the two chambers are brought into communication for the purpose of activation of the capsule.
In both cases, a dedicated working step which has to be carried out manually is required for activation of the capsule. Furthermore, a gas cushion is required in order to allow the reduction in volume which is required for removal of the cover.
In a multicomponent mixer capsule for dental purposes which is known from DE 94 00 374 U1, a first component is contained in a mixing chamber and a second, liquid component is contained in a film bag which is arranged in an auxiliary chamber which is separated from the mixing chamber by a displaceable wall element. A cylindrical mixing body which is present in the mixing chamber is used to displace the wall element at the start of the mixing operation and thus to compress the film bag, so that the latter bursts open and releases the liquid component through a liquid passage which is present in the wall element.
One difficulty of this device consists in designing the wall element, the film bag and the capsule itself in such a way and in dimensioning these components with sufficiently low tolerances for the wall element to be held in its starting position while the capsule is being stored and transported but to be displaced sufficiently far and with such force, under the action of the mixing body, that the film bag bursts open. In this context, it should be borne in mind that the fact that the film bag is often only partially emptied leads to undesirable changes in the mixing ratio and therefore to deterioration in the properties of the finished mixture. Another drawback is that this arrangement is only suitable for mixing, but not for application of the paste.
DE 93 03 268 U1 describes a multicomponent mixer capsule with ejection device for a mixed compound, primarily for dental purposes. This mixer capsule has an activation mandrel which is located in the interior of the capsule and is anchored against the direction of ejection by means of holders in the interior of the capsule body, and a liquid compartment, which is accommodated in the interior of a ram and is sealed with respect to the activation mandrel by a destructible membrane. The activation mandrel fits flush into the empty vessel in the interior of the ram and seals the latter while the material is being forced out. While the material is being forced out in the longitudinal direction, the liquid passes through the thin capillary, which comes to lie in the interior of the activation mandrel, into the mixing space. It is explained that, even during the mixing operation in a vibration mixer and during the discharge of the compound via the ejection nozzle, a small residue of liquid, which is not precisely reproducible, always remains in the capillary. This impairs the quality of the results of mixing.
Consequently, the present invention is based on the object of providing an improved mixer capsule which avoids the abovementioned problems without impairing the desired results of mixing.
This object is achieved by a mixer capsule and a mixer unit which includes this mixer capsule as described in the claims.
The mixer capsule according to the invention has, inter alia, the following advantages:
The moveable body which is present in the mixer capsule serves not only to activate the capsule by destroying the separating device and to assist the mixing operation, but also as a displacement body during emptying.
Since, in the starting state, the body is situated in the main chamber, the activation preferably takes place automatically at the start of the mixing operation, by contrast to the activation steps known from the prior art, which have to be carried out manually.
Since, furthermore, the auxiliary chamber is separated from the main chamber by the separating device through which the body can penetrate, during the subsequent mixing operation it forms part of the mixing chamber itself. This ensures that the second component, which is contained in the auxiliary chamber, completely enters the mixture which is being formed.
Moreover, the unification of main chamber and auxiliary chamber advantageously increases the mixing volume available.
In the final phase of the discharge operation, the body assists with the virtually complete emptying of the interior of the mixer capsule which is formed by the main chamber and auxiliary chamber.
A further advantage is the small number and simple design of the components of the mixer capsule.
The moveable body is preferably of spherical design. The diameter of the ball preferably lies in the range from 4-10 mm, particularly preferably in the range from 5-8 mm.
The weight of the moveable body is adjusted to the condition of the separating device in such a manner that, during normal transport and normal handling, the separating device is not damaged by the moveable body. The separating device can only be penetrated once acceleration values of, for example, 100-500 g (1 g=9.81 msxe2x88x922), preferably 200-400 g, which customarily occur in capsule mixer units are reached.
The auxiliary chamber is preferably in the shape of a hemisphere with a radius which is slightly larger than that of the body. This is favorable for the mixer capsule to be emptied with the minimum possible amount of residues.
It is advantageous if the separating device adheres to an annular surface, which delimits the auxiliary chamber, of the piston and the transition between the annular surface and the inner wall of the auxiliary chamber has a sharp-edged region.
This sharp-edged region preferably runs over a part of the circumference, preferably over substantially 60xc2x0-120xc2x0, particularly preferably from 70xc2x0-90xc2x0. The transition between annular surface and the inner wall of the auxiliary chamber is preferably rounded in the remaining region. This embodiment prevents the foil from tearing off altogether.
In a particular embodiment, the separating device has a desired breaking point, which contributes to controlled and reliable opening of the auxiliary chamber. The prior damage to the separating device or the preparation of a desired breaking point can be effected, for example, by radiation, such as laser radiation, mechanically by scoring or incision using a blade, or thermally by partial fusion or scoring using a heatable blade.
The preparation is preferably carried out only on the plastic part, which may be present, of the separating device, i.e. on the substrate material which is present on one or both sides of a metal layer or SiOx-containing layer. As a result, the seal of the optionally present metal-containing or SiOx-containing layer is maintained.
The preparation can be of any desired shape, but is preferably in a shape which prevents the separating device or parts of this device from tearing off after or during penetration of the separating device by the body. It has proven expedient for the separating device to be prepared in the form of two or more lines which cross one another in the axis of symmetry of the capsule.
In this case, the separating layer only bursts open at a defined location. This prevents the separating layer or parts of this layer from entering the mixture and impeding the discharge operation.
A further advantage of a desired breaking point produced in this way is that even relatively thick foils in the range from 50-80 xcexcm, preferably 60-70 xcexcm can be penetrated with little force (lower mass of the body).
The separating device is preferably in the form of a single-layer or multilayer film or foil, particularly preferably in the form of a composite film or foil or a sealing film or foil. The film or foil preferably comprises at least one metal layer, such as for example an aluminum layer, and at least one, if appropriate two, three or more, plastic layers.
Examples of suitable plastics are: PE, PP, PET, PTFE, PVC, polyamides.
Furthermore, instead of or in addition to the metal foil, the separating device may have plasma-polymerized layers, such as hydrocarbon-containing layers or ceramic barrier layers, such as SiOx layers.
The separating device is attached to the annular end face of the piston, for example by heat-sealing, adhesive bonding, ultrasonic welding or high-frequency welding.
Furthermore, to hold a third component, the separating device may, for example, be designed in the form of a film or foil cushion.
Advantageous materials for the piston of the mixer capsule include metals, such as anodized aluminum, glass, ceramic such as zirconia, plastics and/orxe2x80x94 to reduce permeabilityxe2x80x94plastics which may have undergone metalization or vapor deposition or coating with other materials which have a barrier action. Examples of possible plastics include: PE, PP, PET, PTFE, PVC, EVA, polyamides.
Furthermore, combinations of the abovementioned materials, such as a metal insert, preferably made from aluminum, which is surrounded on the outside and on the inside by the plastic, are conceivable. Parts of this type can be produced using the injection-molding process.
The piston may be produced using a two-component injection-molding process. In this process, first of all, by way of example, an inlay is produced, around which, by way of example, PE is then injection-molded.
High-density plastics, such as PTFE, glass, ceramic, for example zirconia, metals which may be plastic-coated or stainless steel are suitable for the body of the mixer capsule.
The components which are contained in the main chamber, the auxiliary chamber and/or, if appropriate, in the separation device, include both liquids and solids, preferably in powder form. However, base substances in paste form are also possible.
The solids comprise inert fillers, such as finely ground quartz, SiOx-containing substances, glass materials and surface-modified reactive fillers.
The liquids comprise in particular matrix-forming polymerizable substances, for example polyacids comprising acrylic acid derivatives, methacrylic acid derivatives and maleic acid derivatives, as well as copolymers thereof.
The discharge spout on the mixer capsule may be fitted eccentrically to the main chamber. It may also be advantageous to form one or more channels which open into the discharge spout. A design of this type may be expedient for undisturbed emptying of the mixer capsule.
Furthermore, the discharge spout is preferably of closeable design. Possible embodiments are described, for example, in EP-A-0 157 121, in which the discharge spout is pivotably mounted, so that it is closed or open depending on the position of the discharge spout. It is also conceivable to use a spout displacement cap in order to close the discharge spout.